The inkjet printers of today typically use a multi-color printing system. Borders and text are often created with a black printhead, while colors are created by mixing or combining dots from a Black (K), a Cyan (C), a Magenta (M), and a Yellow (Y) printhead.
Drop volume is one measure of a quantity of ink as ejected from an ink nozzle during a single firing. This may also be expressed as “drop weight”, which is the weight of the quantity of ink ejected from an ink nozzle during a single firing. Although this value is reasonably constant for each printhead, it is nearly impossible to manufacture these printheads such that they are exactly the same drop volume every time. Naturally, for print quality control, a narrow range of drop volume, or drop weight, values is acceptable for each printhead. But even with this narrow control range, if one color is on the high end of its acceptable range and another color of printhead is on the low end of its acceptable range, the resultant color may not be the color the user was expecting. For example, if the Cyan printhead is on the high end of its acceptable range, and the Yellow printhead is on the low end of its acceptable range, and the desired color is a true green, the color produced will most likely look more blue-green than true green.
Drop volume/drop weight variations can also be a result of environmental changes to the ink supply, thereby changing the characteristics of the ink; environmental changes to the components of the printhead, both while in storage and in the printer; or from build up of ink in and around the ink firing chambers and nozzles, lessening the volume of ink available to be fired. If any one of the color printheads experiences change in drop volume/drop weight, the result will be a hue, or gradation of color, shift toward the color of the printhead having the higher drop volume.
To minimize the manufacturing variations, a tighter manufacturing tolerance could be enforced. Unfortunately, this typically results in an increased cost to manufacture the printheads. To lessen the environmental effects while the printheads are in the printer, more environmental control (e.g., temperature, humidity, etc.) could be implemented in the printer. This, however, would add to the component and manufacturing costs of the printer and limit its usefulness to only tightly controlled environments.
With the increasing use of inkjet printers for photo quality color printing in the home and in the office, it is desirable for the user to have the ability to calibrate the color in their printer to achieve the “true colors” they desire. Whether the correction is necessary for the above mentioned drop volume/drop weight variations or for personal color preferences of the user, the solution should to be of little or no expense to the user and easily implemented.